CVE-2021-39164: Infoleak
First published: Tue Aug 31 2021(Updated: )
Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the membership (list of members, with their display names) of a room if they know the ID of the room. The vulnerability is limited to rooms with `shared` history visibility. Furthermore, the unauthorised user must be using an account on a vulnerable homeserver that is in the room. Server administrators should upgrade to 1.41.1 or later in order to receive the patch. One workaround is available. Administrators of servers that use a reverse proxy could, with potentially unacceptable loss of functionality, block the endpoints: `/_matrix/client/r0/rooms/{room_id}/members` with `at` query parameter, and `/_matrix/client/unstable/rooms/{room_id}/members` with `at` query parameter.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Matrix Synapse | <1.41.1 | |
| Fedoraproject Fedora | =34 | |
| Fedoraproject Fedora | =35 |
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Reference Links
- https://github.com/matrix-org/synapse/commit/cb35df940a
- https://github.com/matrix-org/synapse/releases/tag/v1.41.1
- https://github.com/matrix-org/synapse/security/advisories/GHSA-3x4c-pq33-4w3q
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2VHDEPCZ22GJFMZCWA2XZAGPOEV72POF/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PXT7ID7DNBRN2TVTETU3SYQHJKEG6PXN/
Frequently Asked Questions
What is CVE-2021-39164?
CVE-2021-39164 is a vulnerability in Matrix Synapse versions 1.41.0 and prior that allows unauthorized users to access the membership (list of members) of a room if they know the room ID and the room has shared history enabled.
What is the severity of CVE-2021-39164?
The severity of CVE-2021-39164 is low, with a CVSS severity score of 3.1.
How can unauthorized users access the membership of a vulnerable room in Matrix Synapse?
Unauthorized users can access the membership of a vulnerable room in Matrix Synapse if they know the room ID and the room has shared history enabled.
Which versions of Matrix Synapse are affected by CVE-2021-39164?
Matrix Synapse versions 1.41.0 and prior are affected by CVE-2021-39164.
How can I fix CVE-2021-39164 in Matrix Synapse?
To fix CVE-2021-39164, upgrade to version 1.41.1 or later of Matrix Synapse.
- collector/nvd-index
- agent/event
- vendor/matrix
- canonical/matrix synapse
- vendor/fedoraproject
- canonical/fedoraproject fedora
- version/fedoraproject fedora/34
- version/fedoraproject fedora/35